Abstract

Vocalizations of koalas are classified as follows: squeak, the basic call of cubs; squawk, a sign of mild distress or aggression; low grunt, the response to very weak stimulus contrast; harsh grunt, of fighting males. All these are poorly structured, with many overlapping frequencies; they are not discrete but are linked by intermediates. The snarl, wail and scream are agonistic calls made by females: the snarl is brief and guttural, the others prolonged and well structured, with distinct harmonics; all three serve as defensive threats only. The bellow is the characteristic male call, and consists of a long series of deep, snoring inhalations and belching exhalations. It is most frequent during the mating season, and is fully developed at 3 years old. Females bellow less often and more softly. The context of all agonistic calls is analysed; those of females are related to the degree of excitement and the nature of the stimulus; bellowing is related to the presence or apparent absence of stimulus and the degree of motivation. Bellowing probably functions as a general broadcast vocalization, evolved from a call made during aggression.